UKIP has earned the right to be taken seriously. But, having won the spotlight he so craves, Nigel Farage can’t duck scrutiny of his policies, as he tried recently, by claiming like some gap-year hippy that UKIP represents a ‘state of mind’.

Farage fears scrutiny of his agenda more than anything. A recently leaked memo found him fretting that UKIP aren’t ‘passing the credibility test’ because of their addiction to ‘promising the earth to everybody’. As if to prove the point, Farage cynically suggested last week that UKIP might ditch support for a state-funded NHS in favour of health insurance, once the election is out the way. Yet, if he really thinks the NHS model is bust, why is he now that promising UKIP would funnel £5 billion extra per year into the current system? Farage knows such flip-flopping is kryptonite for a party that set itself up as the lonely insurgent against a political class that never keeps its promises. And yet, this aqua-planing over the NHS is not a one-off.

In 2010, UKIP’s manifesto promised to introduce a flat tax, invest in not one but three high-speed rail lines, and introduce vouchers so people can opt out of state healthcare or schooling for the private sector. Every party revises policy before a new election. But it’s striking how diametrically opposed UKIP’s new policy of increasing the NHS budget is from the last (and future) one, and how Damascene the conversion against high-speed rail has been. Farage glibly explains he never read the 2010 manifesto, trashing it as ‘486 pages of drivel … a nonsense’ – revealing an unrivalled contempt for the promises he makes to voters at election time.

While Farage has worked hard to professionalise UKIP since 2010, the flip-flopping has only got worse. When newly-defected UKIP MP, Mark Reckless, touted UKIP’s policy of repatriating EU nationals after a Brexit, Farage denounced the policy as ‘unfair, un-British and wrong’. When UKIP’s economics spokesman announced extra VAT on luxury goods – the so-called ‘WAG tax’ – Farage slapped him down. Farage publicly disowned UKIP’s policy of scrapping sex education for children under 11. And there’s been zig-zagging on welfare and the state pension too.

The truth is, confronted by the challenge of turning popular frustration with politics into a clear and positive agenda of its own, UKIP has no guiding lights. Expediency isn’t a great look for any politician. But, it’s arsenic for the guy claiming to “represent a broadly based body of public opinion in this country that recognises the extent to which our political class have betrayed us”. ‘Yo-yo’ politics is buttressed by UKIP’s cake-and-eat-it economics.

Last week, Farage promised to tackle both the ‘cost of living’ and ‘cost of government’ crisis – without explaining how he can pay for it. On generous assumptions, UKIP’s current proposals to extend the personal allowance (to minimum wage levels), cut income tax, abolish inheritance tax, cut fuel duty, and scrap green taxes and Air Passenger Duty would cost £28billion. At the same time, UKIP talks about reinstating the spare room subsidy, increasing job seekers allowance, raising NHS spending, more pothole repairs, cutting tuition fees for STEM students, ending hospital car park fees, more border police and increasing defence spending – costing at least another £14billion.

Even if their savings from scrapping HS2, leaving the EU, slashing the aid budget, curtailing child benefit and foreigners’ access to the NHS held water, it leaves a £17billion black hole. And that doesn’t take into account UKIP’s flirtation with re-nationalising the railways – which Alistair Darling, Labour’s former Transport Secretary, costed at £22 billion back in 2004. Ed Miliband may have forgotten to mention the deficit in his conference speech. But, UKIP don’t have any recognisable deficit policy – and couldn’t deliver on it, if they did.

Farage’s challenge is to turn a movement that feeds off angst into a credible, positive, alternative. There’s no sign of that yet. And a double-talking, flip-flopping, party of spendthrifts will aggravate – not salve – public mistrust of the political class. The only question is how quickly they are rumbled.